A self-countersinking, self-tapping screw for fibrous material such as wood, wood-like materials and composite materials is disclosed in Applicant's own Canadian Patent 2,198,832 (Walther et al.) which issued Apr. 16, 2002. This self-countersinking screw includes an inverted-conical head portion with a cavity adapted to receive a tip of a screwdriver and with a conical bottom having a plurality of triangular recesses each having a lateral side extending inwardly to form a sharp edge and a space for receiving chips. The sharp edge is designed to create a countersink when the screw penetrates into the workpiece. This self-countersinking screw can be inserted easily and efficiently.
One persistent problem with wood screws (or screws for any other fibrous material) is that they have a propensity to loosen over time. It would thus be highly desirable to provide an improved screw for fibrous material that not only is self-countersinking but is also less prone to loosening.